Long pentraxin PTX3 is identified by differential screening from a cDNA phage library made up of human endothelial cells (HUVEC) submitted to treatment with IL1β (Breviario, et al., 1992, J. Biol. Chem., 267: 22190-22197). Its nucleotide sequence is disclosed in the NCBI database under access number X63613. The cDNA of PTX3 codes for a protein of 381 amino acid residues characterised by a signal peptide for the secretion (residues 1-17), by an N-terminal domain (residues 18-178) and by a C-terminal domain (residues 179-381). The gene of human long pentraxin PTX3 maps on chromosome 3 in the q25.2 region and is characterised by 3 exons located on 6.72 kb of genomic DNA.
Recombinant PTX3, purified from the supernatant of CHO cells stably infected with the plasmid vector pSG5h-PTX3 containing the human cDNA of PTX3, analysed by SDS-PAGE in reducing conditions, presents an apparent molecular weight of 45 kDa (Bottazzi, et al., J. Biol. Chem., 1997; 272: 32817-32823). Its amino acid sequence shows a potential glycosylation site at residue 220. The treatment of PTX3 with N-glycosidase F leads to the reduction of its molecular weight to approximately 42 kDa (estimated by SDS-PAGE) in agreement with the value calculated on the basis of the amino acid sequence alone.
This result confirms that PTX3 is N-glycosylated with a sugar contribution amounting to approximately 12% of the molecular weight. Analysis of the protein analysed by SDS-PAGE in non-reducing conditions yielded a molecular weight of approximately 450 kDa (Bottazzi, et al., J. Biol. Chem., 1997; 272: 32817-32823). These results clearly indicate that PTX3 is mainly organised in a decameric structure through the formation of intermolecular disulphide bridges between the cysteine residues of the individual monomers.
However, the deglycoslation protocol proposed in the above-mentioned paper does not permit the preparation of a functionally active PTX3, in view of the fact that, for this to be done, both denaturation and reduction of the disulphide bridges of the protein are necessary.
The protein obtained according to Bottazzi et al.'s method cannot be used as a medicament, having lost its functional characteristics. No use of the deglycosylated pentraxin is, however, suggested.
The present invention solves the problem by providing functionally active deglycosylated pentraxin PTX3.
For a review of the pentraxins, see H. Gewurz, et al., Current Opinion in Immunology, 1995, 7:54-64.
Previous uses of PTX3 are well known.
International patent application WO 99/32516, filed in the name of the present applicant, discloses long pentraxin PTX3 and its use for the therapy of infectious or inflammatory diseases or tumours.
WO 02/38169 discloses the use of long pentraxin PTX3 for the preparation of a medicament useful for the treatment of diseases associated with abnormal activation of growth factor FGF-2.
The treatment of autoimmune diseases by means of the use of long pentraxin PTX3 is disclosed in WO 02/36151.
WO 03/011326 discloses the use of long pentraxin PTX3 for the treatment of female infertility.
WO 03/084561 discloses the use of long pentraxin PTX3 for the preparation of a medicament for the treatment of tumours associated with abnormal activation of growth factor FGF-8.
WO 03/072603 discloses the use of long pentraxin PTX3 for the preparation of autologous vaccines for the treatment of tumours.
PTX3 shares with the short pentraxins CRP and SAP the ability to bind C1q, a component of the complement system. The binding of PTX3 to C1q is saturated with a Kd of 7.4×10−8 M. Kinetic studies of the bimolecular interaction between PTX3 and C1q carried out using the BIAcore have made it possible to measure a Kon of 2.4×105 M−1s−1 and a Koff of 4×10−4 s−1 (Bottazzi, et al., J. Biol. Chem., 1997; 272: 32817-32823).
The comparative analysis of the sequence homology between PTX3 and short pentraxins has revealed a substantial homology of the C-terminal domain of PTX3 with the entire sequence of CRP and SAP (Breviario, et al., 1992, J. Biol. Chem., 267: 22190-22197). Both CRP and SAP compete for the binding of C1q to PTX3, suggesting that the pentraxins recognise the same region on C1q and that the C-terminal domain of PTX3 is the binding site for C1q. In-vitro studies have shown that PTX3 activates the classic complement pathway.
Experimental and clinical evidence shows that functional abnormalities of complement are associated with a greater proneness to infection by pathogens, thus demonstrating an essential function of this innate immune system in protection against infections (Roos, et al., 2002, Immunobiol., 205: 595-609). In the medical field, then, there is a strongly perceived need for drugs capable of boosting and amplifying the immune response to complement-mediated microbial infections.
Moreover, experts in the field are looking for drugs which are increasingly active and capable of acting in synergy with other drugs.